He is a director at a large hospital and the father of Kōko Kaga.
He dresses like a director would, with high classed clothing that consists of a black suit with a striped tie.
He is a firm man who stated that his daughter was a fool. He also has a great sense of responsibility when he apologizes to the owner of the bike that was stolen by Koko, and the parents of 2D-kun when the car is damaged and to Chinami Oka for her wounds, even though he comes from such a rich family. He is also very good natured as he is not willing to bother other people such as telling Banri that his daughter will bring him, who is such a nice guy, troubles.
As said by Mitsuo, Koko's parents and Mitsuo's parents have known each other for a long time.
He appeared after Koko was taken to the police station for allegedly stealing a bicycle to pursue Banri. He appeared and introduced himself as William Van Zant Kaga and once the issue of bike stealing was resolved, he brought Koko home and spoke to Banri. After hitting Koko on the head, he stated that his daughter was very stupid and thanked Banri for being Koko's friend but was interrupted by Koko who said Banri was her boyfriend, not just her friend. He later appears after the car accident where Van Zant slaps Koko hard making her cry for her doings. When Banri went to Koko's house, he is seen driving his car then stops when he saw Banri. He went up with Banri to Koko's room. He later arrives and sees Koko hugging Banri and telling him not to leave her while Banri is speechless when Koko saw her Van Zant. He then assigns Banri to cook meal for them. Hours passed and Van Zant meets Banri, who drives Banri home. Along the way, Banri deduces that Koko may already had knowledge of Banri taking anti-anxiety medications and is asking her father of the diagnosis that leads to its prescription.